wrote

If it is labeled USP, it has to be medical grade or someone will be
sued. BTW if you go in the back of a hospital you will see "welding"
bottles hooked up to their system.


Not only have I looked at the back of the hospital, I've hooked up the
bottles. I've also filled thousands of bottles for medical use. Every one
has a tag with the purity listed and usually a traceability batch number.
Oxygen is oxygen, but unless it has proper certification, it is not for
medical use.

The content may be the same, but the paperwork is not. Without the proper
paperwork, it is not medical grade.